In the islet southeast of Tatarasuna, you'll find a two-part Cube puzzle that connects to another islet that lives between Kannazuka and Seirai Island. Traverse between the two using Thunder Spheres to solve the puzzle.
Start by heading to the area circled in the image below. The arrow demonstrates your travel path upon following the Thunder Spheres.
In the marked-up area, you'll find two Cubes and a Thunder Sakura Bough in-between. The two Cubes have been numbered in the image below for your reference.
Related: How to solve the Light-Up Tile puzzle in Koseki Village Genshin Impact
First, hit Cube 1 with a Normal Attack once to cause a second petal to light up in Cube 1 and a third petal to light up in Cube 2. After, interact with the Thunder Sakura Bough to pick up an Electrogranum and use it to traverse the line of Thunder Spheres that will appear in the sky.
You'll land on an islet further southeast, halfway to Seirai Island. Assuming that the Phase Gate is behind you, hit Cube 2 once to light up all three petals in both Cubes, completing the puzzle. You'll be rewarded with an Exquisite Chest. As with any other puzzle, if you make a mistake, simply teleport away or relog to reset the puzzle and try again.
If you're aiming for 100 percent exploration, make sure to check out our other Genshin Impact puzzle guides, including our guide on How to solve the Cube puzzle between Tatarasuna and Nazuchi Beach in Genshin Impact.
Nicki is a freelance writer with 5 years of writing experience. She's a fan of anything from HoYoverse, from Genshin Impact to Tears of Themis and Honkai: Star Rail. She also loves rhythm games like BanG Dream! and D4DJ.